I. Field of the Invention
This invention relates to a novel reagent and method for the preparation of cationic starches and to the cationic starches thus produced. More particularly, the invention relates to cationic starch derivatives formed by treating starch with the reaction product of a 2,3-dihalopropionamide with a secondary amine.
II. Brief Description of the Prior Art
The modification of starch by chemical derivatization to produce various cationic starches is well known. Cationic starches, i.e. starches which have been modified so that they have a positive electrostatic charge, are used for a large number of applications and are particularly useful in the manufacture of paper due to their greater retention on the paper web as compared to unmodified starches.
A similar starch modification reagent prepared from the reaction of a 2,3-dihalopropionic acid or alkyl ester thereof with a secondary amine has been disclosed in my co-pending application Ser. No. 639,490 filed Dec. 10, 1975 now U.S. Pat. No. 4,017,460. The starch derivatives disclosed therein differ from those of the present invention in that the former are zwitterions and are characterized by the presence of both a cationic and an anionic substituent group on the same reaction site while the starch derivatives of the present invention differ in structure possessing only a cationic substituent as is evidenced by the fact that they are cationic up to about pH 8.2.